Is Male Rheumatoid Arthritis an Occupational Disease? A Review

Exposure to air pollutants and rheumatoid arthritis biomarkers: A scoping review

INTRODUCTION

Rheumatoid arthritis (RA) is a common autoimmune disease with a complex and poorly understood etiology that includes genetic, hormonal, and environmental factors.

OBJECTIVE

Our objective was to assess current literature that investigated the association between exposure to environmental and occupational air pollutants and RA-related biomarkers rheumatoid factor (RF) and anti-citrullinated peptide antibody (ACPA).

DESIGN

PubMed and Web of Science were used to identify epidemiological studies that measured or estimated air pollution and at least one RA biomarker. Information was charted for comparison of evidence, including pollutant(s) studied, exposure assessment, biomarker measurement, analysis method, study population, size, dates, adjustment variables, and findings.

RESULTS

Several common air pollutants (including two mixtures) and a few dozen occupational inhalants were assessed in 13 eligible studies. Associations between industrial sulfur dioxide and particulate matter less than 2.5 µm in diameter with ACPA were observed most frequently, including associations between residential proximity to pollution sources and ACPA positivity. Consistency of associations with other pollutants was either not observed or limited to single studies. Three studies evaluated the modifying impact of SE alleles (a genetic factor associated with RA) and found that pollutant associations were stronger among participants positive for SE alleles.

CONCLUSION

Based on mixed results, there was no consistent link between any single pollutant and RA-related biomarker outcomes. Comparisons across studies were limited by differences in study populations (e.g., by RA status, by sociodemographic groups) and study design (including designs focused on different sources of air pollution, methodological approaches with varying levels of potential exposure misclassification, and assessments of inconsistent biomarker cut-points). However, given that multiple studies reported associations between exposure to air pollution and RA biomarkers, continued exploration utilizing studies that can be designed with a more robust causal framework, including continued consideration of effect modification by genetic status, may be necessary.

Assessment of Risk of Rheumatoid Arthritis Among Underground Hard Rock and Other Mining Industry Workers in Colorado, New Mexico, and Utah

IMPORTANCE

Respirable silica exposure has been strongly and consistently linked to rheumatoid arthritis (RA) among foundry workers, persons in the construction trades, stone crushers and drillers, and coal miners. However, risk of RA in hard rock mining has not been thoroughly investigated.

OBJECTIVE

To analyze occupational risk of RA in hard rock miners in Colorado, New Mexico, and Utah.

DESIGN, SETTING, AND PARTICIPANTS

This cross-sectional survey study estimated the association between mining industry work and reported RA in a random-digit telephone survey of men 50 years or older living in selected counties with elevated levels of pneumoconiosis mortality (N = 1988). The survey was conducted between January 12 and May 4, 2021.

EXPOSURES

Underground hard rock and other mining and related mineral-processing occupations.

MAIN OUTCOMES AND MEASURES

Report of a clinician diagnosis of RA further defined by treatment with corticosteroids or disease-modifying antirheumatic drugs. Risk was estimated using logistic regression.

RESULTS

The analytic sample of 1988 men (survey response rate, 11.1% of all contacts) had a mean (SD) age of 68.6 (10.1) years. Underground hard rock mining was reported by 118 (5.9%); underground mining of other types, predominantly coal mining (no concomitant hard rock), 62 (3.1%); and surface mining or ore processing (no underground), 262 (13.2%). Adjusting for age and smoking and accounting for nonmining silica exposure, mining employment was associated with increased odds of corticosteroid-treated RA (n = 89) (odds ratio, 4.12 [95%, 2.49-6.81]). The odds were similar for RA treated with disease-modifying antirheumatic drugs (n = 80) (odds ratio, 3.30 [95% CI, 1.93-5.66]).

CONCLUSIONS AND RELEVANCE

In this cross-sectional survey study, workers in hard rock and other underground mining and surface mining occupations experienced 3- to 4-fold increased odds of RA. These findings suggest that clinicians should consider patients with relevant work exposures as at higher risk for developing RA.

Cadmium Body Burden and Inflammatory Arthritis: A Pilot Study in Patients from Lower Silesia, Poland

The purpose of this study was to determine the relationship between cadmium exposure and the likelihood of developing or exacerbating symptoms of inflammatory arthritis (IA). The study included 51 IA patients and 46 control subjects. Demographic and lifestyle data were collected. Haematological and biochemical parameters and blood cadmium levels (Cd-B) were determined. Cd-B correlated positively with age, smoking, living in a high-traffic area, and serum levels of inflammatory markers and negatively with mean corpuscular haemoglobin concentration (MCHC). The binary logistic regression model implied that high Cd-B (≥0.65 μg/L) is linked with an increased risk of IA in the studied population (odds ratio: 4.4). High levels of DNA oxidative damage marker (8-hydroxy-2’-deoxyguanosine) (≥7.66 ng/mL) and cyclooxygenase-2 (≥22.9 ng/mL) and frequent consumption of offal was also associated with increased risk of IA. High Cd-B was related to increased risk of disease symptoms onset in the group of IA patients, decreased the level of interleukin 10, and positively correlated with the disease activity. Increased Cd-B is associated with intensified inflammatory processes and decreased haemoglobin levels; in IA patients with decreased anti-inflammatory interleukin 10. These changes partly explain why cadmium exposure and a high cadmium body burden may raise the risk of IA and of disease symptoms exacerbation.

Dusty trades and associated rheumatoid arthritis in a population-based study in the coal mining counties of Appalachia

OBJECTIVES

We previously showed increased coal mining-associated risk of rheumatoid arthritis (RA). Using additional survey data, we sought to delineate this risk further.

METHODS

We used data from two cross-sectional, random-digit-dial, population-based surveys (males;≥50 years) in selected counties in the Appalachian region of the inland, mid-Atlantic USA with elevated pneumoconiosis mortality. Surveys ascertained age, smoking, coal mining and non-coal silica exposure jobs. In a subset, we surveyed ergonomic exposures, scored by intensity. We queried diagnosis of RA, corticosteroid use, and, in a subset, use of disease modifying antirheumatic drugs (DMARDs). Multivariable logistic regression modelled RA risk (defined by glucocorticoid or DMARDs use) associated with coal mining employment, other silica exposure, smoking status, and age and ergonomic exposures.

RESULTS

We analysed data for 2981 survey respondents (mean age 66.6 years; 15% current, 44% ex-smokers). The prevalence of glucocorticoid-treated and DMARD-treated RA was 11% and 4%, respectively. Glucocorticoid-treated RA was associated with coal mining (OR 3.5; 95% CI 2.5 to 4.9) and non-coal mining silica exposure (OR 3.2; 95% CI 2.4 to 4.4). For DMARD-treated RA, the odds associated with coal mining and other silica remained elevated: OR 2.3 (95% CI 1.18, 4.5) and OR 2.7 (95% CI 1.51, 5.0), respectively. In the same model, the highest intensity ergonomic exposure also was associated with increased odds of RA (OR 4.3; 95% CI 1.96 to 9.6).

CONCLUSIONS

We observed a strong association between coal mining and other silica-exposing dusty trades and RA. Clinicians and insurers should consider occupational histories in the aetiology of RA.

Increased susceptibility to organic dust exposure-induced inflammatory lung disease with enhanced rheumatoid arthritis-associated autoantigen expression in HLA-DR4 transgenic mice

Immunogenetic as well as environmental and occupational exposures have been linked to the development of rheumatoid arthritis (RA), RA-associated lung disease, and other primary lung disorders. Importantly, various inhalants can trigger post-translational protein modifications, resulting in lung autoantigen expression capable of stimulating pro-inflammatory and/or pro-fibrotic immune responses. To further elucidate gene-environment interactions contributing to pathologic lung inflammation, we exploited an established model of organic dust extract (ODE) exposure with and without collagen-induced arthritis (CIA) in C57BL/6 wild type (WT) versus HLA-DR4 transgenic mice. ODE-induced airway infiltration driven by neutrophils was significantly increased in DR4 versus WT mice, with corresponding increases in bronchoalveolar lavage fluid (BALF) levels of TNF-⍺, IL-6, and IL-33. Lung histopathology demonstrated increased number of ectopic lymphoid aggregates comprised of T and B cells following ODE exposure in DR4 mice. ODE also induced citrullination, malondialdehyde acetaldehyde (MAA) modification, and vimentin expression that co-localized with MAA and was enhanced in DR4 mice. Serum and BALF anti-MAA antibodies were strikingly increased in ODE-treated DR4 mice. Coupling ODE exposure with Type II collagen immunization (CIA) resulted in similarly augmented pro-inflammatory lung profiles in DR4 mice (relative to WT mice) that was accompanied by a profound increase in infiltrating lung CD4⁺ and CD8⁺ T cells as well as CD19⁺CD11b⁺ autoimmune B cells. Neither modeling strategy induced significant arthritis. These findings support a model in which environmental insults trigger enhanced post-translational protein modification and lung inflammation sharing immunopathological features with RA-associated lung disease in the selected immunogenetic background of HLA-DR4 mice.

The impact of airborne endotoxin exposure on rheumatoid arthritis-related joint damage, autoantigen expression, autoimmunity, and lung disease

Airborne biohazards are risk factors in the development and severity of rheumatoid arthritis (RA) and RA-associated lung disease, yet the mechanisms explaining this relationship remain unclear. Lipopolysaccharide (LPS, endotoxin) is a ubiquitous inflammatory agent in numerous environmental and occupational air pollutant settings recognized to induce airway inflammation. Combining repetitive LPS inhalation exposures with the collagen induced arthritis (CIA) model, DBA1/J mice were assigned to either: sham (saline injection/saline inhalation), CIA (CIA/saline), LPS (saline/LPS 100 ng inhalation), or CIA + LPS for 5 weeks. Serum anti-citrullinated (CIT) protein antibody (ACPA) and anti-malondialdehyde-acetaldehyde (MAA) antibodies were strikingly potentiated with co-exposure (CIA + LPS). CIT- and MAA-modified lung proteins were increased with co-exposure and co-localized across treatment groups. Inhaled LPS exacerbated arthritis with CIA + LPS > LPS > CIA versus sham. Periarticular bone loss was demonstrated in CIA and CIA + LPS but not in LPS alone. LPS induced airway inflammation and neutrophil infiltrates were reduced with co-exposure (CIA + LPS). Potentially signaling transition to pro-fibrotic processes, there were increased infiltrates of activated CD11c+CD11b+ macrophages and transitioning CD11c+CD11bint monocyte-macrophage populations with CIA + LPS. Moreover, several lung remodeling proteins including fibronectin and matrix metalloproteinases as well as complement C5a were potentiated with CIA + LPS compared to other treatment groups. IL-33 concentrations in lung homogenates were enhanced with CIA + LPS with IL-33 lung staining driven by LPS. IL-33 expression was also significantly increased in lung tissues from patients with RA-associated lung disease (N = 8) versus controls (N = 7). These findings suggest that patients with RA may be more susceptible to developing interstitial lung disease following airborne biohazard exposures enriched in LPS.

Work disability and rheumatoid arthritis: Predictive factors

BACKGROUND

Rheumatoid arthritis is often associated with work disability, a term used to describe the inability to be or to remain employed. Work disability is a common implication of rheumatoid arthritis.

OBJECTIVE

This review aims to identify and analyze the predictive factors of work disability among patients with rheumatoid arthritis, as well as to group these factors into broader categories, based on the most current studies in this field.

METHODS

An electronic search was conducted using Google Scholar, MEDLINE and PsycINFO databases. Eighty-six international journal articles were finally selected.

RESULTS

The results suggest that occupational, personal, medical and societal factors are the main predictive categories of work disability for people with rheumatoid arthritis.

CONCLUSIONS

Medical progress has had a positive effect on the development and the rates of work disability among patients with RA. Work disability is, however, not only defined by medical factors. Occupational, personal and societal factors interact with each other and affect the development of work disability in RA. The results of this review emphasize the need for medical and vocational therapy interventions, social support and state policies that target the work status of patients with RA. Future holistic research approaches to the field are required for a complete picture and concrete solutions with the aim of keeping patients with RA employed.

Evaluation of C-Reactive Protein and Associated Factors Among Patients Suffering from Rheumatoid Arthritis at Tikur Anbessa Specialized Hospital, Addis Ababa, Ethiopia

Background

Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory disorder, which is associated with increased pro-inflammatory mediators to induce an elevation in acute-phase response, migration of immune cells and swelling of synovial joints. Evaluation of the level of C-reactive protein and associated risk factors in RA patients was the main aim of this study. Identifying the association between disease activity of RA (hsCRP) and socio-demographic characteristics was another aim of the study.

Methods

Institution-based cross-sectional study was conducted at the Rheumatology Clinic of Tikur Anbessa Specialized Hospital. In this study, the level of hsCRP was measured in both case and control groups. Simple descriptive statistics, multivariate analysis, independent sample t-test were utilized for statistical analysis. The strength of association between different risk factors and hsCRP was measured using odds ratio and 95% confidence interval. P-value < 0.05 was considered as statistically significant.

Result

The result of this study showed that the hsCRP level was significantly higher among RA patients as compared to the control groups (P-value = 0.004). There was an association between smoking and high disease activity status (AOR= 20.03, p= 0.40). Low economic status had a statistically significant association with high hsCRP level (AOR = 12.79, p=0.00). In this study, 42 RA patients had >3mg/l hsCRP level with different occupational exposures. On the other hand, 31 RA patients had <3mg/l hsCRP level among different exposures. Although there was no statistically significant association, the association between associated risk factors (oil consumption, physical exercise, educational status) and disease activity was computed in this study.

Conclusion

The inflammatory marker, hsCRP was significantly higher among patients as compared to controls. The higher hsCRP showed a high grade of systemic inflammation in RA patients. C-reactive protein was elevated in rheumatoid factor positive patients and patients with high BMI value. Additionally, the result of our study showed that different socio-economic factors had an association with disease activity of RA.

Association of Agricultural, Occupational, and Military Inhalants With Autoantibodies and Disease Features in US Veterans With Rheumatoid Arthritis

OBJECTIVE

To determine the association of inhalant exposures with rheumatoid arthritis (RA)-related autoantibodies and severity in US veterans.

METHODS

Participants in the Veterans Affairs Rheumatoid Arthritis (VARA) registry were mailed surveys assessing occupational, agricultural, and military inhalant exposures. Demographic characteristics, disease activity, functional status, and extraarticular features were obtained from the VARA registry, while HLA-DRB1 shared epitope (SE) status, anti-cyclic citrullinated peptide (anti-CCP) antibodies, and rheumatoid factor (RF) were measured using banked DNA/serum from enrollment. Associations between inhalant exposures and RA-related factors (autoantibodies, severity, and extraarticular features) were assessed using multivariable linear and logistic regression models adjusted for age, sex, race, and tobacco use and stratified by SE status. Adjusted odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated.

RESULTS

Questionnaires were returned by 797 of 1,566 participants (50.9%). Survey respondents were older, more often White or male, and less frequently smokers, and had lower disease activity compared to nonrespondents. Anti-CCP positivity was more common among veterans exposed to burn pits (OR 1.66 [95% CI 1.02, 2.69]) and military waste disposal (OR 1.74 [95% CI 1.04, 2.93]) independent of other factors. Among participants who were positive for SE alleles, burn pit exposure (OR 5.69 [95% CI 2.73, 11.87]) and military waste disposal exposure (OR 5.05 [95% CI 2.42, 10.54]) were numerically more strongly associated with anti-CCP positivity. Several inhalant exposures were associated with the presence of chronic lung disease, but not with the presence of RF or the level of disease activity.

CONCLUSION

Military burn pit exposure and military waste disposal exposure were independently associated with the presence of anti-CCP antibodies in RA patients. These findings are consistent with emerging evidence that various inhalant exposures influence autoantibody expression and RA risk.

High-throughput analysis of lung immune cells in a combined murine model of agriculture dust-triggered airway inflammation with rheumatoid arthritis

Rheumatoid arthritis (RA)-associated lung disease is a leading cause of mortality in RA, yet the mechanisms linking lung disease and RA remain unknown. Using an established murine model of RA-associated lung disease combining collagen-induced arthritis (CIA) with organic dust extract (ODE)-induced airway inflammation, differences among lung immune cell populations were analyzed by single cell RNA-sequencing. Additionally, four lung myeloid-derived immune cell populations including macrophages, monocytes/macrophages, monocytes, and neutrophils were isolated by fluorescence cell sorting and gene expression was determined by NanoString analysis. Unsupervised clustering revealed 14 discrete clusters among Sham, CIA, ODE, and CIA+ODE treatment groups: 3 neutrophils (inflammatory, resident/transitional, autoreactive/suppressor), 5 macrophages (airspace, differentiating/recruited, recruited, resident/interstitial, and proliferative airspace), 2 T-cells (differentiating and effector), and a single cluster each of inflammatory monocytes, dendritic cells, B-cells and natural killer cells. Inflammatory monocytes, autoreactive/suppressor neutrophils, and recruited/differentiating macrophages were predominant with arthritis induction (CIA and CIA+ODE). By specific lung cell isolation, several interferon-related and autoimmune genes were disproportionately expressed among CIA and CIA+ODE (e.g. Oasl1, Oas2, Ifit3, Gbp2, Ifi44, and Zbp1), corresponding to RA and RA-associated lung disease. Monocytic myeloid-derived suppressor cells were reduced, while complement genes (e.g. C1s1 and Cfb) were uniquely increased in CIA+ODE mice across cell populations. Recruited and inflammatory macrophages/monocytes and neutrophils expressing interferon-, autoimmune-, and complement-related genes might contribute towards pro-fibrotic inflammatory lung responses following airborne biohazard exposures in setting of autoimmune arthritis and could be predictive and/or targeted to reduce disease burden.

Inhalants other than personal cigarette smoking and risk for developing rheumatoid arthritis

PURPOSE OF REVIEW

The current review summarizes the current evidence on inhalants other than personal cigarette smoking and risk for developing rheumatoid arthritis (RA).

RECENT FINDINGS

Personal cigarette smoking has been implicated as an environmental risk factor for seropositive RA, perhaps by inducing autoimmunity at pulmonary mucosa. Since many patients with RA are nonsmokers, other inhalants are being investigated as potential RA risk factors. Recent case-control and cohort studies have investigated passive cigarette smoking, air pollution, inhalant-related occupations, silica, pesticides, household environment, and allergic inhalants as inhalant exposures for RA risk. Inhalant-related occupations and silica inhalants have the most consistent evidence for associations with increased RA risk. However, most studies relied on retrospective designs and had limited ability to adjust for personal cigarette smoking or investigate associations among nonsmokers.

SUMMARY

Several inhalants other than personal cigarette smoking may be associated with increased risk for developing RA. These results support the hypothesis that inhalants, pulmonary mucosal inflammation, and RA pathogenesis may be linked. Future studies are needed to firmly establish the independence of these findings from personal cigarette smoking and to determine the specific inhalants and biologic mechanisms related to RA pathogenesis.

Long-term exposure to a mixture of industrial SO2, NO2, and PM2.5 and anti-citrullinated protein antibody positivity

BACKGROUND

Studies of associations between industrial air emissions and rheumatic diseases, or diseases-related serological biomarkers, are few. Moreover, previous evaluations typically studied individual (not mixed) emissions. We investigated associations between individual and combined exposures to industrial sulfur dioxide (SO₂), nitrogen dioxide (NO₂), and fine particles matter (PM_2.5) on anti-citrullinated protein antibodies (ACPA), a characteristic biomarker for rheumatoid arthritis (RA).

METHODS

Serum ACPA was determined for 7600 randomly selected CARTaGENE general population subjects in Quebec, Canada. Industrial SO₂, NO₂, and PM_2.5 concentrations, estimated by the California Puff (CALPUFF) atmospheric dispersion model, were assigned based on residential postal codes at the time of sera collection. Single-exposure logistic regressions were performed for ACPA positivity defined by 20 U/ml, 40 U/ml, and 60 U/ml thresholds, adjusting for age, sex, French Canadian origin, smoking, and family income. Associations between regional overall PM_2.5 exposure and ACPA positivity were also investigated. The associations between the combined three industrial exposures and the ACPA positivity were assessed by weighted quantile sum (WQS) regressions.

RESULTS

Significant associations between individual industrial exposures and ACPA positivity defined by the 20 U/ml threshold were seen with single-exposure logistic regression models, for industrial emissions of PM_2.5 (odds ratio, OR = 1.19, 95% confidence intervals, CI: 1.04-1.36) and SO₂ (OR = 1.03, 95% CI: 1.00-1.06), without clear associations for NO₂ (OR = 1.01, 95% CI: 0.86-1.17). Similar findings were seen for the 40 U/ml threshold, although at 60 U/ml, the results were very imprecise. The WQS model demonstrated a positive relationship between combined industrial exposures and ACPA positivity (OR = 1.36, 95% CI: 1.10-1.69 at 20 U/ml) and suggested that industrial PM_2.5 may have a closer association with ACPA positivity than the other exposures. Again, similar findings were seen with the 40 U/ml threshold, though 60 U/ml results were imprecise. No clear association between ACPA and regional overall PM_2.5 exposure was seen.

CONCLUSIONS

We noted positive associations between ACPA and industrial emissions of PM_2.5 and SO₂. Industrial PM_2.5 exposure may play a particularly important role in this regard.

Combined Collagen-Induced Arthritis and Organic Dust-Induced Airway Inflammation to Model Inflammatory Lung Disease in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is characterized by extra-articular involvement including lung disease, yet the mechanisms linking the two conditions are poorly understood. The collagen-induced arthritis (CIA) model was combined with the organic dust extract (ODE) airway inflammatory model to assess bone/joint-lung inflammatory outcomes. DBA/1J mice were intranasally treated with saline or ODE daily for 5 weeks. CIA was induced on days 1 and 21. Treatment groups included sham (saline injection/saline inhalation), CIA (CIA/saline), ODE (saline/ODE), and CIA +  ODE (CIA/ODE). Arthritis inflammatory scores, bones, bronchoalveolar lavage fluid, lung tissues, and serum were assessed. In DBA/1J male mice, arthritis was increased in CIA +  ODE >  CIA >  ODE versus sham. Micro-computed tomography (µCT) demonstrated that loss of BMD and volume and deterioration of bone microarchitecture was greatest in CIA +  ODE. However, ODE-induced airway neutrophil influx and inflammatory cytokine/chemokine levels in lavage fluids were increased in ODE >  CIA +  ODE versus sham. Activated lung CD11c+ CD11b+ macrophages were increased in ODE >  CIA +  ODE >  CIA pattern, whereas lung hyaluronan, fibronectin, and amphiregulin levels were greatest in CIA +  ODE. Serum autoantibody and inflammatory marker concentrations varied among experimental groups. Compared with male mice, female mice showed less articular and pulmonary disease. The interaction of inhalation-induced airway inflammation and arthritis induction resulted in compartmentalized responses with the greatest degree of arthritis and bone loss in male mice with combined exposures. Data also support suppression of the lung inflammatory response, but increases in extracellular matrix protein deposition/interstitial disease in the setting of arthritis. This coexposure model could be exploited to better understand and treat RA-lung disease. © 2019 American Society for Bone and Mineral Research.

Genistein inhibits angiogenesis developed during rheumatoid arthritis through the IL-6/JAK2/STAT3/VEGF signalling pathway

Background

Angiogenesis plays an important role in the development of rheumatoid arthritis (RA), which increases the supply of nutrients, cytokines, and inflammatory cells to the synovial membrane. Genistein (GEN), a soy-derived isoflavone, has been validated that can effectively inhibit the angiogenesis of several tumours. We thus carried out a study in vitro to investigate the effect of GEN in vascular endothelial growth factor (VEGF) expression and angiogenesis induced by the inflammatory environment of RA.

Methods

MH7A cells were used to verify whether GEN can inhibit the expression of VEGF in MH7A cells under inflammatory conditions and demonstrate the mechanism. EA.hy926 ​cells were used to verify whether GEN can inhibit the migration and tube formation of vascular endothelial cells in inflammatory environment.

Results

GEN dose-dependently inhibited the expression and secretion of interleukin (IL)-6 and VEGF, as well as the nucleus translocation of Signal transducer and activator of transcription 3 (STAT3) in MH7A. Furthermore, GEN inhibited IL-6-induced vascular endothelial cell migration and tube formation in vitro.

Conclusion

GEN inhibits IL-6-induced VEGF expression and angiogenesis partially through the Janus kinase 2 (JAK2)/STAT3 pathway in RA, which has provided a novel insight into the antiangiogenic activity of GEN in RA.

The translational potential of this article

Our study provides scientific guidance for the clinical translational research of GEN in the RA treatment.

Prevalence of Arthritis and Rheumatoid Arthritis in Coal Mining Counties of the United States

OBJECTIVE

Exposure to inhaled mineral dust, in particular silica, is associated with increased odds of rheumatoid arthritis (RA) and other autoimmune diseases. We studied the association of RA with work-related coal and silica exposure in the Appalachian region of the US.

METHODS

We carried out a random-digit dialed telephone survey in selected counties in Appalachia that had elevated coal workers' pneumoconiosis mortality. Our study cohort included men ages ≥50 with any employment history, and we assessed exposure to coal mining employment, other work-related dust, and ergonomic factors. We ascertained self-reported physician diagnosis of any arthritis and of RA with glucocorticoid treatment. We used multivariable logistic regression analysis to estimate the odds ratios (ORs) and associated population attributable fraction (PAF) estimates.

RESULTS

Among the 973 men who met study entry criteria (mean ± SD ages 66 ± 10 years; 54% ever smokers), 266 (27%) reported coal mining work and 189 (19%) reported other work-related silica exposure. There were 517 men (53%), who reported any arthritis and 112 (12%) whose disease met the study definition of RA. Adjusting for covariates, coal mining was associated with elevated odds of RA (OR 3.6 [95% confidence interval (95% CI) 2.1-6.2]), which accounted for a PAF of 33% (95% CI 26-40%) of the men studied. For any arthritis, the coal mining-associated OR was 2.3 (95% CI 1.6-3.2), with an associated PAF of 20% (95% CI 14-25%).

CONCLUSION

In this population of older males living in a coal mining region, we estimated that 20% of arthritis and 33% of RA may be attributable to coal mining work.

Mucosa-Environment Interactions in the Pathogenesis of Rheumatoid Arthritis

Mucosal surfaces play a central role in the pathogenesis of rheumatoid arthritis (RA). Several risk factors, such as cigarette smoking, environmental pollution, and periodontitis interact with the host at the mucosal level, triggering immune system activation. Moreover, the alteration of microbiota homeostasis is gaining increased attention for its involvement in the disease pathogenesis, modulating the immune cell response at a local and subsequently at a systemic level. Currently, the onset of the clinical manifest arthritis is thought to be the last step of a series of pathogenic events lasting years. The positivity for anti-citrullinated protein antibodies (ACPAs) and rheumatoid factor (RF), in absence of symptoms, characterizes a preclinical phase of RA-namely systemic autoimmune phase- which is at high risk for disease progression. Several immune abnormalities, such as local ACPA production, increased T cell polarization towards a pro-inflammatory phenotype, and innate immune cell activation can be documented in at-risk subjects. Many of these abnormalities are direct consequences of the interaction between the environment and the host, which takes place at the mucosal level. The purpose of this review is to describe the humoral and cellular immune abnormalities detected in subjects at risk of RA, highlighting their origin from the mucosa-environment interaction.

Prevalence of rheumatoid arthritis in relation to serum cadmium concentrations: cross-sectional study using Korean National Health and Nutrition Examination Survey (KNHANES) data

OBJECTIVES

It has been suggested that exposure to heavy metal cadmium (Cd) may contribute to a high risk of developing rheumatoid arthritis (RA). This study was to investigate the association of RA prevalence and serum concentrations of Cd and other heavy metals through large survey data analysis.

DESIGN

A retrospective cross-sectional survey study.

SETTING

Large population survey in Korea.

PARTICIPANTS

53 829 subjects participated in Korean National Health and Nutrition Examination Survey (KNHANES) from 2008 to 2013.

INTERVENTIONS

Heavy metals were measured in different time periods of the survey programme which resulted in three different data sets for analysis: Cd, mercury (Hg) and lead (Pb) from 2008 to 2012 survey; serum manganese (Mn) and urine arsenic (As) from 2008 to 2009 survey; and serum zinc (Zn) from 2010 survey. RA prevalence and its associations with serum heavy metals were analysed using a general linear/logistic regression model of complex sample design.

RESULTS

Serum Cd was elevated in patients with RA (RA vs control: 1.30±0.07 µg/L vs 1.17±0.01 µg/L, p<0.01). There were no significant differences in urine levels of As or serum levels of Pb, Hg, Mn or Zn between patients with RA and controls. OR (95% CI) of RA prevalence according to 1 µg/L increase of serum Cd level was 1.28(95% CI 1.03 to 1.61). Prevalence of RA in women was increased with increasing quartiles of Cd levels, with a 19-fold difference in female RA prevalence between individuals in the lowest quartile of serum Cd level and those in the highest quartile (0.18% vs 3.42%). Cubic spline curve of prevalence OR showed increased risk of RA according to increased serum Cd level. Increased risk of RA in men was not observed with increased serum Cd levels.

CONCLUSION

There was an increased prevalence of RA in females associated with increased serum levels of Cd in the Korean population.

Sex differences impact the lung-bone inflammatory response to repetitive inhalant lipopolysaccharide exposures in mice

Skeletal health consequences associated with inflammatory diseases of the airways significantly contribute to morbidity. Sex differences have been described independently for lung and bone diseases. Repetitive inhalant exposure to lipopolysaccharide (LPS) induces bone loss and deterioration in male mice, but comparison effects in females are unknown. Using an intranasal inhalation exposure model, 8-week-old C57BL/6 male and female mice were treated daily with LPS (100 ng) or saline for 3 weeks. Bronchoalveolar lavage fluids, lung tissues, tibias, bone marrow cells, and blood were collected. LPS-induced airway neutrophil influx, interleukin (IL)-6 and neutrophil chemoattractant levels, and bronchiolar inflammation were exaggerated in male animals as compared to female mice. Trabecular bone micro-CT imaging and analysis of the proximal tibia were conducted. Inhalant LPS exposures lead to deterioration of bone quality only in male mice (not females) marked by decreased bone mineral density, bone volume/tissue volume ratio, trabecular thickness and number, and increased bone surface-to-bone volume ratio. Serum pentraxin-2 levels were modulated by sex differences and LPS exposure. In proof-of-concept studies, ovarectomized female mice demonstrated LPS-induced bone deterioration, and estradiol supplementation of ovarectomized female mice and control male mice protected against LPS-induced bone deterioration findings. Collectively, sex-specific differences exist in LPS-induced airway inflammatory consequences with significant differences found in bone quantity and quality parameters. Male mice demonstrated susceptibility to bone loss and female animals were protected, which was modulated by estrogen. Therefore, sex differences influence the biologic response in the lung-bone inflammatory axis in response to inhalant LPS exposures.

Vapour, gas, dust and fume occupational exposures in male patients with rheumatoid arthritis resident in Cornwall (UK) and their association with rheumatoid factor and anti-cyclic protein antibodies: a retrospective clinical study

OBJECTIVES

To quantify exposure to vapour, gas, dust and fumes (VGDF) and smoking in male rheumatoid arthritis (RA) and investigate impact on rheumatoid factor (RF) and anti-citrullinated protein antibody (ACPA) levels.

DESIGN

A retrospective observational study.

SETTING

The Royal Cornwall Hospital Trust, UK. A single university hospital setting.

PARTICIPANTS

726 men followed up between February 2015 and August 2016, fulfilling RA diagnostic criteria.

MAIN OUTCOME MEASURES

Prevalence of VGDF exposure and smoking prior to RA diagnosis. Determination of association between VGDF, smoking and autoantibody levels.

RESULTS

546/726 (75%) had been exposed to VGDF for >1 year. 561/726 (77%) had been smokers. Only 58/726 (8%) had no exposure to VGDF and had never smoked. A significant difference in RF levels was observed between unexposed and VGDF exposed never smokers (median RF 24 vs 36, p=0.03), more marked when comparing unexposed with ≥2 VGDF exposures (median RF 24 vs 57, p=0.02). A significant difference in RF levels was also observed between unexposed and VGDF exposed smokers (median RF 71 vs RF 95, p=0.04), more marked when comparing unexposed with ≥2 VGDF exposures (median RF 71 vs RF 113, p=0.01). A significant difference in RF titre was observed between never smokers >2 VGDF exposures and smokers with >2 VGDF exposures (RF 57 vs RF 113, p=0.02). No association of ACPA seropositivity rates or titres with VGDF exposure was observed. Smokers with >2 VGDF exposures had a significantly lower age of RA diagnosis than smokers with no VGDF exposure (53 years vs 57 years, p=0.03). All results remained similar when corrected for social class.

CONCLUSIONS

VGDF exposure increases RF levels. Combination exposure to smoking and VDGF results in higher RF levels, particularly with multiple exposures. These compelling findings demonstrate the importance of combined inhaled exposures in RF generation.

DNA methylation in human diseases

Even though the importance of epigenetics was first recognized in light of its role in tissue development, an increasing amount of evidence has shown that it also plays an important role in the development and progression of many common diseases. We discuss some recent findings on one representative epigenetic modification, DNA methylation, in some common diseases. While many new risk factors have been identified through the population-based epigenetic epidemiologic studies on the role of epigenetics in common diseases, this relatively new field still faces many unique challenges. Here, we describe those promises and unique challenges of epigenetic epidemiological studies and propose some potential solutions.

The Effect of Inhalant Organic Dust on Bone Health

PURPOSE OF REVIEW

Agriculture remains a major economic sector globally, and workers experience high rates of chronic inflammatory lung and musculoskeletal diseases. Whereas obstructive pulmonary diseases are known risk factors for bone loss, the underlying relationship between lung inflammation and bone health is not well known.

RECENT FINDINGS

An agriculture organic dust extract inhalation animal model has recently linked lung injury-induced inflammation to systemic bone loss. This process is dependent upon lipopolysaccharide and the toll-like receptor 4 (TLR4) signaling pathway. Downstream systemic interleukin-6 is a key mediator that subsequently activates osteoclastogenesis. Age is a host factor that impacted bone disease with younger mice demonstrating increased susceptibility to bone loss following inhalant exposures as compared to older mice. Supplemental dietary vitamin D was shown to prevent organic dust-induced bone loss, but not lung disease, in animals. Recent animal studies provide new mechanistic insight into the lung-bone inflammatory axis. Host factors, diet, and lipopolysaccharide/TLR4 signaling pathways play a significant role in explaining how inhalant organic dust exposures impact bone health. These investigations might lead to specific targeted therapeutic approaches.

Cadmium nanoparticles citrullinate cytokeratins within lung epithelial cells: cadmium as a potential cause of citrullination in chronic obstructive pulmonary disease

Objective

The objective of the study was to determine whether the cadmium-derived materials induce intracellular protein citrullination.

Methods

Human A549 lung epithelial cells were exposed to cadmium in soluble and nanoparticulate forms represented by cadmium chloride (CdCl₂) and cadmium oxide (CdO), respectively, and their combinations with ultrafine carbon black (ufCB) produced by high temperature combustion, imitating cigarette burning. Protein citrullination in cell lysates was analyzed by Western immunoblotting and verified by immunofluorescent confocal microscopy. Target citrullinated proteins were identified by proteomic analysis.

Results

CdO, ufCB and its combination with CdCl₂ and CdO after high temperature combustion induced protein citrullination in cultured human lung epithelial cells, as detected by immunoblotting with anti-citrullinated protein antibody. Cytokeratins of type II (1, 2, 5, 6A, 6B and 77) and type I (9, 10) were identified as major intracellular citrullination targets. Immunofluorescent staining confirmed the localization of citrullinated proteins both in the cytoplasm and cell nuclei.

Conclusion

Cadmium oxide nanoparticle exposure facilitated post-translational citrullination of proteins.